Method and apparatus for monitoring ingestion of medications using an implantable medical device

ABSTRACT

An implantable medical device, such as a pacemaker or implantable cardioverter defibrillator (ICD), is configured to automatically detect ingestion of medications to verify that prescribed medications are taken in a timely manner and at the correct dosage. Briefly, individual pills are provided with miniature radio frequency identification (RFID) devices capable of transmitting RFID tag signals, which identify the medication contained within the pill and its dosage. The implanted device is equipped with an RFID transceiver for receiving tag signals from a pill as it is being ingested. The implanted system decodes the tag to identify the medication and its dosage, then accesses an onboard database to verify that the medication being ingested was in fact prescribed to the patient and to verify that the correct dosage was taken. Warning signals are generated if the wrong medication or the wrong dosage was taken. Therapy may also be automatically adjusted. Non-RF-based ID devices are also described, which instead transmit ID data via biphasic current pulses.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/985,298, filed Nov. 9, 2004, and now U.S. Pat. No. 7,414,534.

FIELD OF THE INVENTION

The invention generally relates to implantable medical devices and totechniques for verifying ingestion of prescribed medications using suchdevices.

BACKGROUND OF THE INVENTION

Every year, countless medications are prescribed to millions of patientsto address a wide variety of medical conditions. It is often difficult,however, for physicians to ensure that appropriate dosages of prescribedmedications are actually taken by their patients at the appropriatetimes. Many patients simply fail to take prescribed drugs—sometimesintentionally (perhaps because they want to avoid perceived side effectsof the drugs)—sometimes unintentionally (perhaps because they simplyforget to take the drugs or run out of the drugs). In other cases, theprescribed drug is taken, but with an incorrect dosage level. This mayoccur because the patient believes, contrary to the advice of thephysician, that a stronger dosage would be beneficial or, moretypically, because the patient has simply forgotten that he or she hadalready taken the medication and then takes an additional, unnecessarydose. These problems are particularly significant among the elderly, whomay have a large number of ongoing prescriptions at any one time and whooften show signs of short term memory loss. For many medical conditions,including serious heart conditions such as congestive heart failure(CHF), failure to take the prescribed dosage of the drug in a timelymanner can have severe adverse consequences. Accordingly, it would behighly desirable to provide techniques, particularly for the benefit ofthe elderly, for automatically monitoring prescription drug intake toremind the patient if he or she has failed to take a prescribed drug ina timely manner or to warn the patient if the incorrect drug orincorrect dosage has been taken. It is to this end that the invention isgenerally directed.

Many elderly patients have implanted medical devices, such as pacemakersor implantable cardioverter defibrillators (ICDs), or are candidates forsuch devices. Increasingly, such devices are provided with thecapability of generating warning signals to alert the patient to adversemedical conditions, such as the onset of particular heart problems, sothat medical attention may be sought. See, for example, U.S. patentapplication Ser. No. 10/603,429, filed Jun. 24, 2003 of Wang, et al.,entitled “System and Method for Detecting Cardiac Ischemia Using anImplantable Medical Device”. Depending upon the implanted system, thewarning signals may be transmitted to an external bedside monitor foralerting the patient or may be applied internally in the form of aperceptible warning signal generated, for example, by an implantedvibration device. In any case, it would be desirable to equipimplantable medical devices with components for automatically monitoringprescription drug intake so that such warning devices can also be usedto alert the patient if he or she fails to take a prescribed drug in atimely manner or takes the incorrect dosage of the drug. It is to thesespecific ends that particular aspects of the invention are directed.

SUMMARY

In accordance with one embodiment, a technique is provided for use indetecting the ingestion of drugs by a patient in which an implantablemedical system is implanted. The implanted system senses a signaltransmitted by an individual pill as it is being ingested and therebydetects ingestion of the pill based on the sensed signal.

In one example, individual pills are provided with miniature radiofrequency identification (RFID) devices capable of transmitting RFID tagsignals, which identify the medication contained within each respectivepill, as well as its dosage. The implanted system is equipped with anRFID transceiver (or receiver in the case of active RFID medications)for sensing RFID tag signals emitted by the RFID device in the pill asit is being ingested. The implanted system decodes the RFID tag toidentify the medication of the pill and its dosage. The device thenaccesses an onboard database listing patient prescriptions to verifythat the medication being ingested was in fact prescribed to the patientand to verify that the correct dosage was taken. Warning signals aregenerated via an internal warning device or via a bedside monitor toalert the patient in case the wrong medication or the wrong dosage wastaken. The device also periodically accesses the on-board database toidentify any medications that were prescribed to the patient but werenot taken in a timely manner and, if so, reminder signals are generated,again using either an implanted warning device, bedside monitor, orboth. If a bedside monitor is provided, the bedside monitor preferablyforwards the various warning or reminder signals to the prescribingphysician so he or she may be alerted as well. This is particularlydesirable if it has been found that the patient has taken the wrongmedication.

Preferably, the RFID device of each pill is coated with a suitablehermetic substance, such as ceramic, so as to be biocompatible andnon-digestible. After the pill has been digested, the RFID device of thepill is merely passed from the body as waste and thereby discarded. Forcapsules, the circuitry of the RFID device may be formed on a flexiblesubstrate that is wrapped around the perimeter of the capsule. Fordisk-shaped tablets, the circuitry of the RFID device may be attached toa flat base of the tablet. In any case, the RFID device preferablytransmits the RFID tag via low frequency RF signals, which are capableof passing through the tissues of the patient from the esophageal trackto the RFID transceiver of the implanted system.

The RFID devices in the pills may be passive or active. A passive RFIDdevice has no on-board battery and transmits its RFID tag only inresponse to the temporary delivery of power from an RFID transceiver. Anactive RFID device has an on-board battery and transmits its RFID tagperiodically, in which case the implanted device may simply include anRFID receiver as opposed to an RFID transceiver. For use with pillsequipped with passive RFID devices, the RFID transceiver of theimplanted system uses an antenna to transmit power to the pill via lowfrequency RF signals. The RFID device of the pill then uses the receivedpower to transmit the RFID tag back to the transceiver. To reduce powerconsumption, the implanted system is preferably equipped with componentscapable of detecting when the patient is in the act of swallowing andonly transmits RFID power signals via the antenna at such times.Swallowing may be identified, for example, based on certain patientmovements detected by an accelerometer in combination with internalpatient sounds detected by an acoustic sensor and further in combinationwith patient posture as detected by a posture detector. A patient sleepdetector may also be used to detect sleep so as to deactivate the RFIDtransceiver while the patient is sleeping and hence not capable oforally ingesting medications. When used with pills equipped with activeRFID devices, the implanted system may instead continuously monitor forpossible RFID signals from pills being ingested; though, preferably,such monitoring is again only performed while the patient is found to beswallowing, so as to reduce processing demands within the implantedsystem.

In embodiments wherein the implantable system is a pacemaker or ICD, thedrugs to be ingested are often heart medications, such asanti-arrhythmics, anti-thrombolytics, or the like. In such embodiments,if the implanted system determines that the patient has failed to take aprescribed heart medication in a timely manner, the system mayautomatically adjust pacing therapy in an attempt to compensate. Forexample, if the patient fails to take a drug prescribed for reducing therisk of atrial fibrillation (AF), the device may activate overdrivepacing in an attempt to reduce the likelihood that AF will occur. Asanother example, if the patient fails to take a drug prescribed forreducing the risk of ventricular fibrillation (VF), the device maypre-charge a shocking capacitor so that, should a life-threatening VFoccur, a defibrillation shock can be delivered promptly, thus improvingthe patient's chance of survival. If the system is provided with animplanted drug pump, the pump may be controlled to deliver a quantity ofstored medication in an attempt to compensate for medication that shouldhave been taken orally. In this regard, the drug pump may be providedwith a small “reserve” quantity of a critical medication. Hence, shouldthe patient run out of critical medication that is to be taken orally,the implanted system can ensure that the patient receives at least someof the needed medication internally while the patient seeks to obtainmore of the oral medication.

Although well suited for use with pacemakers or ICDs, the invention maybe implemented using any of a wide range of other implantable medicaldevices, such as devices for stimulating or sensing portions of thebrain, spinal cord, muscles, bones, nerves, glands or other body organsor tissues. The invention may alternatively be implemented as adedicated device implanted solely for monitoring the ingestion ofmedications. Moreover, whereas miniaturized RFID devices areparticularly well suited for transmitting suitable ID signals to theimplanted system, other miniaturized transmission devices may instead beemployed, such as non-RF based electronic ID (EID) devices. For example,a pill may be equipped to transmit an ID tag via a sequence of biphasiccurrent pulses, which are conducted through the tissues of the body. Theleads of the pacemaker or ICD are used to sense the biphasic currentpulses so that the ID tag may then be decoded.

Also, whereas the invention is described herein primarily with respectto detecting the ingestion of prescription medications in the form ofpills or tablets, principles of the invention may be applied fordetecting intake of medications consumed via other means or fordetecting the consumption of other items entirely, such as dietarysupplements or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention may be more readilyunderstood by reference to the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 illustrates pertinent components of an implantable RFID-basedmedication monitoring system having a pacemaker or ICD capable ofdetecting RFID tag signals transmitted by pills being ingested so as tomonitor prescription drug intake;

FIG. 2 is a flow chart illustrating, at a high level, an exemplarymethod for automatically monitoring prescription drug intake, whichemploys the implantable system of FIG. 1, wherein warning/remindersignals are generated if the correct dosages of prescribed medicationsare not taken in a timely manner;

FIG. 3 is a block diagram illustrating database components for use withthe technique of FIG. 2 for monitoring prescription drug intake;

FIG. 4 is a flow chart illustrating an exemplary technique for use withthe system of FIG. 1 for detecting intake of pills equipped with passiveRFID devices;

FIG. 5 is a flow chart illustrating an exemplary method for use with thetechnique of FIG. 1 for determining when the patient is in the act ofswallowing for use in triggering a passive RFID device;

FIG. 6 is a flow chart illustrating an exemplary technique for use withthe system of FIG. 1 for detecting intake of pills equipped with activeRFID devices;

FIG. 7 is a flow chart illustrating an exemplary technique for use withthe system of FIG. 1 for detecting if the patient has failed to take aprescribed medication within an expected time frame;

FIG. 8 is a stylized diagram illustrating an individual medicationcapsule equipped with an RFID device for use with the system of FIG. 1;

FIG. 9 is a stylized diagram illustrating an individual medicationtablet equipped with an RFID device for use with the system of FIG. 1;

FIG. 10 is a diagram particularly illustrating functional components ofa pill equipped with a passive RFID device for use with the system ofFIG. 1;

FIG. 11 is a block diagram particularly illustrating functionalcomponents of a pill equipped with an active RFID device for use withthe system of FIG. 1;

FIG. 12 is a simplified diagram illustrating the pacemaker or ICD ofFIG. 1 and its lead system;

FIG. 13 is a block diagram illustrating internal functional componentsof the device of FIG. 12, which includes components for automaticallymonitor drug intake via RFID signals;

FIG. 14 illustrates pertinent components of an implantable medicationmonitoring system having a pacemaker or ICD capable of detecting ID tagsignals transmitted through patient tissue as biphasic current pulses;and

FIG. 15 is a block diagram particularly illustrating functionalcomponents of a pill equipped with biphasic current pulse generator foruse with the system of FIG. 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description includes the best mode presently contemplatedfor practicing the invention. The description is not to be taken in alimiting sense but is made merely for the purpose of describing thegeneral principles of the invention. The scope of the invention shouldbe ascertained with reference to the issued claims. In the descriptionsthat follow, like numerals or reference designators are used to refer tolike parts or elements throughout.

Overview of Implantable RFID-Based Medication Intake Monitoring System

FIG. 1 illustrates an implantable medical system 8 capable of: detectingingestion of RFID-tagged medications; verifying the correct drug/dosageof the ingested medications; delivering any necessary warning orreminder signals if the correct drug/dosage of a prescribed medicationhas not been ingested in a timely manner; and controlling therapy inresponse thereto. Briefly, implanted system 8 includes a pacer/ICD 10 orother implantable medical device that utilizes an RFID transceiver (orsimply a receiver) 12 to detect RFID tag signals from medications beingingested, such as exemplary capsule 14, which is equipped with aminiaturized RFID device 16. Based on the RFID tag, the pacer/ICDdetermines the particular drug and dosage being ingested and comparesthis information against an on-board database listing drugs currentlyprescribed to the patient, the prescribed dosages, and the frequencywith which the drugs should be taken (i.e. once per day, twice per day,etc.) so as to verify that the correct drug is being taken at thecorrect dosage level and at the correct frequency. Assuming that is thecase, the date/time and drug/dosage of the ingested medication arestored within a database maintained within memory of the pacer/ICD.Otherwise, appropriate warning signals and/or reminder signals aregenerated. For example, if the patient fails to take a prescribedmedication in a timely manner, a reminder signal may be generated toremind the patient. If the patient takes the wrong dosage or takes thewrong medication entirely, a warning signal may be generated to alertthe patient. Warning/reminder signals may be generated internally usingan implanted warning/reminder device 18, which may be, for example, avibrating device or a “tickle” voltage warning device providingperceptible stimulation directly to the patient. The warning device maybe part of, or contained in, the pacer/ICD itself. Additionally, or inthe alternative, warning/reminder signals may be transmitted to abedside reminder/warning system 22 for display thereon. The bedsidemonitor may provide audible or visual alarm signals to alert the patientas well as textual or graphic displays.

Depending upon the particular implementation, the bedside system mayalso forward any pertinent warning signals to the physician thatoriginally prescribed the medication so as to advise the physician. Thewarning signals may be relayed via a trans-telephonic system or anyother suitable communication system. In addition, if the patient failsto take a critical medication, an implantable drug pump 24 may beemployed to deliver a reserve quantity of the medication stored thereinto ensure that the patient does not go without the medication for anextended period of time. If the prescribed medication is a heartmedication, such as an anti-arrhythmic or anti-thrombolytic medication,the pacer/ICD may also adjust pacing therapy in an attempt to compensatefor failure to take the prescribed medication. Pacing therapy isdelivered to the heart via a set of implanted leads 26, only two ofwhich are shown in FIG. 1. A full set of leads is illustrated in FIG.12.

For the invention to be most advantageously exploited, all indigestibleprescription medications are preferably provided with miniaturized RFIDdevices, each encoded with an RFID tag identifying the particularmedications contained therein and the dosage. In this manner, anyprescription medication being ingested by the patient can be detectedand identified. Alternatively, only certain critical medications areequipped with RFID devices, i.e. medications that must be taken inprecise dosages in a timely manner to avoid life-threatening conditions.In other cases, only certain classes of medications are equipped withRFID devices. For example, within the field of cardiac rhythmmanagement, it may be sufficient that pills containing selected heartmedications be equipped with RFID devices. In addition, the use ofRFID-based technology is merely exemplary. Any suitable technology maybe used for transmitting appropriate identification signals from a pillbeing ingested to an implanted decoding device. An RFID-based example isdescribed herein since RFID technology is well-suited for use with theinvention, particularly because RFID-based devices may be miniaturizedfor attachment to individual tablets, capsules and the like foringestion.

Thus, FIG. 1 provides an overview of an implantable system formonitoring drug ingestion based on RFID tag signals. Internal signaltransmission lines provided for interconnecting the various componentsof the system are not all shown in the figure. Wireless signaltransmission may alternatively be employed, though care should be takento ensure that any internal wireless transmission signals betweenimplanted components do not interfere with RFID signals. In addition,the particular locations of the implanted components shown in FIG. 1 aremerely illustrative and may not necessarily correspond to actual implantlocations. As will be explained, in some implementations, the RFIDtransceiver is preferably positioned as close to the esophagus orstomach as possible.

Note that embodiments may be implemented that do not necessarilyincorporate all of the components illustrated in FIG. 1. In many cases,for example, the implanted system will include only the pacer/ICD, itsleads and the RFID transceiver, with all warning/reminders transmittedto the bedside system. Drug pumps and internal warning devices are notnecessarily implanted. In other embodiments, the implanted system maypotentially utilize the leads of the pacer/ICD for detecting RFID tagsignals from active RFID devices only, with no separate RFID transceiverprovided for detecting RFID tag signals from passive RFID devices. Instill other embodiments, the implanted system does not employ apacer/ICD at all. Other implantable medical devices may instead beconfigured to perform the RFID-based monitoring techniques of theinvention, such as devices provided for stimulating or sensing thenervous system, muscles, glands, organs, or the like. Alternatively, adedicated device may be implanted solely for the purpose of performingthe RFID-based monitoring techniques of the invention, i.e. a devicethat does not additionally perform any other implantable medical devicefunctions. An RFID device represents just one type of EID device. Othertypes of EID devices may instead be employed. An example involving EIDdevices that transmit signals via biphasic current pulses is describedbelow with reference to FIGS. 14-15.

No attempt is made herein to describe all possible combinations ofcomponents that may be provided in accordance with the invention. Anexample employing a pacer/ICD is described herein since many patientsbenefiting from the ID-based monitoring techniques of the invention areelderly patients who may also require a pacer/ICD to address heartproblems. Hence, by configuring a pacer/ICD to implement the techniqueof the invention, a single system may be implanted that provides bothmedication monitoring and cardiac rhythm management.

Overview of Technique for Monitoring Ingestion of Medications Using anImplanted System

The flow chart of FIG. 2 illustrates a general method for monitoringingestion of prescribed medications using an implantable system. Thismethod may be implemented by the system FIG. 1 or by any other suitableimplantable system. In the flow chart of FIG. 2, operations performed bythe RFID device of a pill being ingested are shown on the left;operations performed by an implanted medical system are shown in themiddle; operations performed by an external bedside warning/reminderdevice are shown on the right. Briefly, beginning at step 100, an RFIDdevice attached to a pill being ingested transmits an RFID signal as itis being ingested. If the RFID device is passive, the RFID signal istransmitted only in response to a query from the implantable system. Ifthe RFID device is active, the RFID signal is instead transmittedperiodically. Particular examples specific to active or passive RFIDdevices are described below. In any case, the implanted system uses itsRFID transceiver to detect the RFID tag signal, at step 102. At step104, the implanted system then accesses on-board databases to verifythat the medication being ingested was prescribed to the patient and toverify that the correct dosage has been taken. Appropriatewarning/reminder signals are transmitted, at step 106, from theimplanted system to the bedside warning/reminder device, which displaysthe warning/reminder for the patient, at step 108 and, optionally,forwards the warning/reminder to the prescribing physician via thepublic switched telephone network (PSTN), the Internet, a wirelesscommunication network, or any other suitable communication network. See,e.g., communication techniques set forth in U.S. Pat. No. 6,249,705,“Distributed Network System for Use with Implantable Medical Devices”.

The bedside monitor provides audible alerts along with textual displays.Depending upon the configuration of the bedside monitor, specifictextual displays may be generated for describing particularwarning/reminders. Some exemplary textual warning/reminders are asfollows:

-   -   Reminder—The correct dosage of the following prescribed drug has        not been taken: PROCAINAMIDE. If you have forgotten to take the        prescribed drug, please do so now.    -   Warning—The following prescribed drug has not been taken:        PROCAINAMIDE. It appears that a different drug has been taken        instead. Please contact your physician immediately.

Preferably, confirmation messages are displayed whenever the correctdrug and dosage has been taken. In that way, if neither a confirmationmessage nor a warning message is displayed following ingestion of a pillequipped with an RFID device, the patient is thereby alerted that themonitoring system may not be functioning properly. Each patient havingan implanted device capable of detecting RFID-equipped pills ispreferably provided with a bedside monitor for installation at his orher home. Additionally, bedside monitors are preferably provided inclinics, hospitals, and the like.

The verification procedure performed at step 104 preferably utilizes aset of databases stored within onboard memory of the implanted system.Exemplary databases are illustrated in FIG. 3. A first database 110provides information relating individual prescription drugs to theunique RFID tags associated therewith. A second database 112 listsparticular medications that have been prescribed to the patient alongwith the prescribed dosage and the prescribed frequency, i.e. “once perday”, “twice per day”, etc. A third database 114 provides a record ofdrugs already ingested, the dosage, and the date/time the drug wastaken. In one example, each RFID tag is a unique 96-bit tag, whichidentifies, at minimum, the medication and its dosage. Other data tagsizes may instead be employed. The length of the data tag to be used maydepend on the total number of unique drug/dosage combinations of pillsexpected to be equipped with RFID tags. If relatively few pills are tobe equipped with RFID tags, then relatively short RFID tags may besufficient to uniquely distinguish one from the other. If a large numberof different pills are to be equipped with RFID tags, then longer RFIDtags may be needed to uniquely distinguish one from the other.Alternatively, each RFID tag may be specific so as to be long enough toadditionally encode a unique serial number identifying the particularpill and its manufacturer for tracking purposes.

To identify a particular pill being ingested, the implanted systemcompares the RFID tag received from the RFID device of the pill againstprescription drug/RFID tag database 110. In the example of FIG. 3,database 110 lists various exemplary dosages of procainamide anddiltiazem, which are anti-arrhythmic heart medications. If, for example,the RFID tag received from the pill being ingested matches the tagassociated with the 375 mg capsule of procainamide, the implanted systemthereby determines that the patient has taken 375 mg of procainamide andrecords that information along with the date/time within the medicationintake record database 114. The system then accesses the patientprescription database 112 to determine whether that particularmedication and dosage had been prescribed to the patient. If not, asuitable warning signal is generated. Periodically, the implanted systemalso examines the patient prescription database to identify anymedications that had been prescribed, but which the patient has nottaken within an expected time frame determined by the prescribedfrequency. In this manner, the system can generate reminder signals forreminding the patient to take the prescribed medication. This will bedescribed in greater detail below with reference to FIG. 7.

In one example, database 110 only lists those medications that have beenprescribed the patient. This minimizes the amount of data to be storedwithin the database. If the RFID tag received from a pill being ingesteddoes not match any of the entries within the database, the implantedsystem generates a warning signal indicating that an “unknown”medication has been ingested. Alternatively, database 110 mayadditionally include RFID tags for any and all medications equipped withRFID devices so that the implanted system can identify the particularmedication that had been erroneously ingested. This allows thephysician, once notified, to evaluate any adverse consequences to thepatient and, in particular, to identify any possible drug interactionproblems with other medications that the patient might be taking.However, a greater amount of device memory is required. In still otherimplementations, the database stores RFID tags for all drugs withincertain classes of medications. For example, if the implanted system isa pacer/ICD, the database may store RFID tags for all heart medications.If the implanted system is instead a system for stimulating portions ofthe nervous system, RFID tags for all drugs directed to treating thenervous system may instead be stored. In any case, the list of drugs tobe stored within database 110 may be recorded therein during devicemanufacture, following device implant via a device programmer, or duringa subsequent follow-up session between patient and physician (again viaa device programmer.)

The list of drugs within database 112 is updated using a deviceprogrammer whenever the physician prescribes new drugs to the patient,changes to the prescribed dosage or frequency, or withdraws any previousprescriptions. In this manner, database 112 is kept up-to-date. Ifdesired, pharmacists may be provided with suitable devices fortransferring prescription data into the implanted system of a patient sothat, whenever a patient picks up a new prescription, the pharmacist canupdate the data stored within the implanted device to reflect thatprescription. Coordination of prescription information by pharmacistsvia RFID devices mounted to pill vials is discussed in U.S. Pat. No.5,963,136 to O'Brien entitled “Interactive Prescription Compliance andLife Safety System.” However, there is no mention therein of mountingRFID devices to the pills themselves for ingestion or of the use of animplantable system for detecting the RFID-equipped pills.

Alternatively, rather than maintaining the databases of FIG. 3 withinthe implanted device itself, the databases are instead maintained withinthe bedside monitor system. Within such an implementation, the implantedsystem merely forwards RFID tags received from pills being ingested tothe bedside monitor, which then accesses the databases stored therein toverify that the correct prescription drug has been taken and to issueany appropriate warning or reminder. This reduces the memory andprocessing requirements of implanted device itself. Assuming theimplanted system is in communication with the bedside monitor at thetime the drug is ingested, the RFID tag is immediately relayed to thebedside monitor so that a warning signal, if needed, may be promptlygenerated. If not, transmission of the RFID tag is deferred until thenext time the implanted system is in communication with the bedsidemonitor. In yet another implementation, if no bedside monitor isprovided, RFID tags for ingested medication are merely stored within theimplanted system until a follow-up session between patient andphysician. At that time, the physician transfers the RFID tags from theimplanted system to the external programmer (along with other storeddiagnostic information) for display thereon. The physician can thenverify that the patient has been properly taking prescribed medications.An implementation wherein the databases are maintained within theimplanted device itself is preferred since it allows therapy (such aspacing therapy) to be immediately adjusted to compensate for failure totake prescribed drugs in a timely manner. In addition, assuming aninternal warning system is employed, warning/reminder signals may beimmediately provided to the patient. Otherwise, warning/reminder signalscan only be provided to the patient after the implanted system hasrelayed data to the bedside monitor for other external systems, whichmay result in a substantial delay.

Also, although primarily described with respect to detecting theingestion of prescription medications in pill form, the techniques ofthe invention described herein are also applicable to detection ofingestion of non-prescription drugs in pill form, as well as otherproducts provided in pill form, such as dietary supplements. Thetechniques of the invention are also applicable to the detection of theingestion of other items or products besides pills, such as quantitiesof liquid medication to be taken orally. For example, a single dosage ofmedication in liquid form may be provided with an RFID device floatingtherein (properly encapsulated), which is then ingested by the patientwhile he or she drinks the medication.

1. Exemplary Technique for Monitoring Ingestion of Medications UsingPassive RFID

FIG. 4 illustrates an exemplary technique for monitoring medicationintake via pills equipped with passive RFID devices, particularly foruse with a pacer/ICD. Briefly, to reduce power consumption within thepacer/ICD, the pacer/ICD seeks to detect when the patient is swallowingand only outputs RFID power signals at such times. Also, with thetechnique of FIG. 4, in addition to generating warning/reminder signals,the technique adjusts pacing therapy to compensate for failure to takeprescribed medications and/or activates an implanted drug pumped todeliver suitable alternate medications, if available.

Beginning at step 200, the pacer/ICD monitors patient motion, posture,etc. to detect when the patient is swallowing. This will be describedmore thoroughly with reference to FIG. 5. Assuming the patient isswallowing, and hence might possibly be swallowing a pill provided witha passive RFID device, the pacer/ICD, at step 202, activates an RFIDpower transmission antenna to transmit power, preferably toward theesophagus and stomach of the patient. In one example, the powertransmission antenna is activated for 15 seconds. If the patient wasindeed swallowing a pill equipped with a passive RFID device, thecircuitry of the pill uses the power received from the pacer/ICD totransmit its encoded RFID tag, which the antenna of the pacer/ICD thendetects. In this regard, the passive RFID device is a so-called“full-duplex” transponder, i.e. an RFID device that transmits the RFIDtag concurrently as it receives power. Alternately, the RFID device maybe a “half-duplex” transponder, i.e. an RFID device that stores receivedpower, then transmits the RFID tag shortly thereafter. Full-duplex ispreferred as it reduces the number of circuit components required on theRFID device. An RFID device with full-duplex circuit components will bedescribed below with reference to FIG. 10. Of course, most of the timethat the patient is swallowing, he or she will merely be ingesting foodor beverage and will not be ingesting an RFID-equipped pill. Hence, noRFID tag signal will be detected by the pacer/ICD at that time.Nevertheless, by activating the power transmission antenna of thepacer/ICD only while the patient is swallowing, substantial powersavings can be achieved as compared to a system that would otherwisetransmit power at all times.

Low-frequency RFID signals are preferably employed, e.g. signalsoperating at about 125 kHz. By using low-frequency signals, the signalscan properly propagate through the tissues of the body. However, lowerfrequencies require generally larger device components and sofrequencies below 125 kHz are not preferable. The transmission power ofthe pacer/ICD and the return transmission power of the RFID device ofthe pill are preferably set to the lowest power levels sufficient toensure that the RFID tag of a pill being ingested will be properlydetected by the pacer/ICD. This helps reduce power consumption by thepacer/ICD as well as reduce the risk that the pacer/ICD mayinadvertently detect the RFID tag of a pill external to the body,perhaps a pill that the patient intends to ingest but then forgets toingest. Optimal transmission power values to be used depend upon thesize, shape and orientation of the antenna of the pacer/ICD, itsproximity to the esophagus and stomach, and characteristics of theintervening tissues, as well as the characteristics of the RFID deviceof the pill. Routine experimentation may be performed to identifyoptimal power transmission levels based upon these parameters. Otherwiseroutine experimentation may be employed to determine appropriate powertransmission levels for the antenna of the pacer/ICD as well asappropriate power transmission levels for the RFID device of the pill.Routine experimentation may also be employed to determine optimalparameters for the size, shape, position and orientation of the antennaof the pacer/ICD. Preferably, following implant of the pacer/ICD, aphysician or other medical professional performs tests to determine theoptimal power level sufficient to ensure reliable detection of pillsbeing ingested by the particular patient in which the pacer/ICD has beenimplanted. The pacer/ICD is then programmed to use the optimal powerlevel. The power level may be increased during a follow-up session ifthe patient complains that the pacer/ICD has failed to detectmedications properly ingested.

Assuming that an RFID tag has been detected then, at step 204, internalcomponents of pacer/ICD compare the RFID tag against the on-boardprescription drug/RFID tag database (i.e. database 110 of FIG. 3) todetermine if it corresponds with any prescription drugs listed therein.If not then, at step 206, a warning is issued indicating that thepatient has ingested an unknown medication, which has not beenprescribed to the patient. Assuming, however, that the RFID tag is foundwithin the database, then at step 208, the pacer/ICD compares themedication and dosage of the pill against the on-board patientprescription database (i.e. database 112 of FIG. 3) to verify that thecorrect drug/dosage as been ingested, and within a proper time frame. Ifso then, at step 210, the pacer/ICD records the date/time anddrug/dosage in the intake record database (i.e. database 114 of FIG. 3).If not, then, at step 212, the pacer/ICD: warns the patient of ingestionof the wrong drug or wrong dosage; automatically adjusts pacing therapyin attempt to compensate for failure to take the correct drug/dosage;and/or controls an implantable drug pump to deliver a reserve quantityof the prescribed medication or an alternate acceptable medication, ifavailable.

Generation of warning signals is discussed above. Insofar as control oftherapy is concerned, the pacer/ICD may adjust pacing control parameters(subject to programming commands previously provided by the physician)in attempt to compensate for failure to take the prescribed drug orfailure to take the correct dosage of the prescribed drug. In oneexample, should the patient fail to take medications intended to reducethe risk of episodes of AF, the pacer/ICD may be programmed toautomatically activate atrial overdrive pacing to compensate. (Overdrivepacing of the atria has been found to be effective in reducing the riskof AF.) Alternatively, if overdrive pacing is already active, thepacer/ICD may increase the aggressiveness overdrive pacing. Aparticularly effective overdrive pacing technique for suppressing AF,referred to as dynamic atrial overdrive (DAO) pacing, is described inU.S. Pat. No. 6,519,493 to Florio et al. See also: U.S. PatentApplication 2003/0130704, also of Florio et al., entitled “Method andApparatus for Dynamically Adjusting a Non-Linear Overdrive PacingResponse Function”, filed Jan. 9, 2002; and U.S. Patent Application2003/0130703, of Florio et al., entitled “Method and Apparatus forDynamically Adjusting Overdrive Pacing Parameters”, filed Jan. 9, 2002.

In another example, should the patient fail to take anti-thrombolyticdrugs intended to reduce the risk of a thrombosis (i.e. a blood clot),the pacer/ICD automatically reduces pacing rates or deactivatesoverdrive pacing, in an attempt to reduce the likelihood of athrombosis. In yet another example, should the patient fail to takemedications intended to reduce the severity of heart failure, thepacer/ICD may automatically activate cardiac resynchronization therapy(CRT) in an attempt to improve heart function. Exemplary heart failuremedications include ACE inhibitors, diuretics, digitalis and compoundssuch as captopril, enalapril, lisinopril and quinapril. CRT and relatedtherapies are discussed in, for example, U.S. Pat. No. 6,643,546 toMathis, et al., entitled “Multi -Electrode Apparatus And Method ForTreatment Of Congestive Heart Failure”; U.S. Pat. No. 6,628,988 toKramer, et al., entitled “Apparatus And Method For Reversal OfMyocardial Remodeling With Electrical Stimulation”; and U.S. Pat. No.6,512,952 to Stahmann, et al., entitled “Method And Apparatus ForMaintaining Synchronized Pacing”. In still another example, if theimplanted system is an ICD and the patient has failed to take drugsprescribed to reduce the risk of an episode of VF, the pacer/ICD may beprogrammed to immediately charge defibrillation capacitors. In thismanner, should an episode of VF occur, the pacer/ICD would be able toimmediately deliver a defibrillation shock, thereby increasing thechances of patient survival.

These are merely a few examples pertaining to heart conditions, whichare particularly useful for implementations employing a pacer/ICD. Ingeneral, a wide variety of pacing and defibrillation control parametersmay potentially be selected by the physician for automatic control basedupon detection of failure to take prescribed medications. For othertypes of implantable medical devices, such as devices that stimulate thenervous system, control parameters specific to those devices may beautomatically adjusted in response to failure to take prescribedmedications. The particular control parameters to be automaticallyadjusted and the form of adjustment depends upon the functionality ofthe implanted device, the prescribed medications and the consequences tothe patient of failure to take the prescribed medications. Those skilledin the art may make those determinations for particular medications andfor use with particular implanted devices.

Insofar as the automatic control of an implanted drug pump is concerned,a drug pump may be provided with a quantity of critical medication suchthat, should the patient fail to take medication (perhaps because he orshe has run out of the oral form of the medication or is incapacitatedand cannot take the medication orally), the drug pump may provide areserve quantity of the drug to ensure that the patient at leastreceives some of the drug. Depending upon the particular medication,alternative compounds may be required for delivery via an implantabledrug pump. Routine experimentation may be employed to identify alternatemedications that are safe and effective for use in connection with animplantable drug pump. Implantable drug pumps are discussed in U.S. Pat.No. 5,328,460 to Lord, et al., entitled “Implantable Medication InfusionPump Including Self-Contained Acoustic Fault Detection Apparatus”.

For implementations wherein the implanted system is a pacer/ICD and theprescribed medications are heart medications, techniques forautomatically evaluating the efficacy of medications based uponexamination of internal electrical cardiac signals may be employed inconjunction with the techniques of the present invention. See, inparticular, U.S. Pat. No. 7,142,911 to Boileau et al., entitled “Methodand Apparatus for Monitoring Drug Effects on Cardiac Electrical SignalsUsing an Implantable Cardiac Stimulation Device,” which is incorporatedby reference herein. Using techniques described in that application, thepacer/ICD may be programmed to automatically detect changes, if any,within the electrical cardiac signals caused by failure to take theprescribed medication. The pacer/ICD preferably postpones any changes topacing control parameters that would otherwise be triggered by failureto take the prescribed medication until a reduction in efficacy becomesapparent based upon an examination of the cardiac signals. In thismanner, the pacer/ICD avoids making any unnecessary changes to controlparameters if there is still sufficient medication within the patient'ssystem to benefit the patient. In addition, an examination of drugefficacy based on cardiac signals serves to confirm an RFID-baseddetection of failure to take prescribed medications. Circumstances mayarise, for example, where the pacer/ICD fails to detect the RFID tag ofa medication that has been properly ingested, perhaps due to a failureof the RFID device of the pill itself. In such circumstances, thepacer/ICD might unnecessarily adjust pacing control parameters. Bydeferring any such adjustments until confirmation is provided based upona drug efficacy analysis, unnecessary adjustments are avoided.

Referring now to FIG. 5, techniques will now be described for detectingwhen the patient is in the act of swallowing, for use at step 200 ofFIG. 4. To detect swallowing, the pacer/ICD simultaneously monitors anumber of patient parameters including patient motion, patient posture,internal patient sounds, and patient sleep/wake cycles. At step 214, forexample, the pacer/ICD employs an accelerometer or other motiondetection device to monitor patient movement to identify a motionsignature consistent with swallowing. In this regard, slight patientmovements and vibrations occurring while swallowing, particularly whileswallowing a relatively large pill, are distinct from other patientmovements. The pacer/ICD stores a motion signature template indicativeof movement occurring during swallowing a pill within onboard memory andcompares patient movements detected by the accelerometer against thetemplate to identify circumstances wherein it appears likely that thepatient is swallowing a pill. Otherwise conventional pattern matchingtechniques may be employed. In one example, following device implant,the patient is asked to swallow one or two pills during which time thepacer/ICD is programmed to detect resulting motions and generate amotion signature for subsequent use. Alternatively, a generalizedsignature applicable to a wide population of patients may instead beemployed. In any case, following step 214, the pacer/ICD generates avalue indicating whether it appears the patient is swallowing a pill ornot. Depending upon the implementation, this value may be used alone orin combination with corroborating parameters for use in activating theRFID device of the pacer/ICD to search for passive RFID tags. In theexample of FIG. 5, corroboration is provided based upon patient posture,internal patient sounds, and patient sleep/wake cycles.

Simultaneously, or alternatively, at step 216, the pacer/ICD employs anacoustic sensor to monitor internal patient sounds (i.e. auscultations)to identify a sound signature consistent with swallowing. As withmovement, internal patient sounds occurring while swallowing,particularly while swallowing a relatively large pill, are generallydistinct from other internal patient sounds. The pacer/ICD stores asound signature template indicative of internal patient sounds occurringwhile swallowing a pill and compares internal patient sounds against thetemplate to identify circumstances wherein it appears likely that thepatient is swallowing a pill. As with movement-based detection, thepatient is preferably asked to swallow one or more pills following thedevice implant during which time the pacer/ICD detects resultinginternal sounds and generates a sound signature for subsequent use.Alternatively, a generalized sound signature applicable to a widepopulation of patients may instead be employed. Acoustic sensors for usewith pacer/ICDs for detecting heart sounds may be adapted for use indetecting sounds associated with swallowing. See, for example, U.S. Pat.Nos. 5,836,987; 5,935,081; 6,477,406; and 6,527,729. Following step 216,the pacer/ICD generates a value indicating whether it appears thepatient is swallowing a large pill or not. Depending upon theimplementation, this value may be used alone or in combination withpatient motion or other corroborating parameters for activating the RFIDdevice.

At step 218, the pacer/ICD tracks patient posture to determine whetherposture is consistent with, or inconsistent with, the act of swallowinga pill. If inconsistent, then a detection of swallowing made based uponpatient movement or internal sounds is ignored. For example, pills arerarely, if ever, swallowed while the patient is prone (i.e. while thepatient lies on his or her stomach). Accordingly, if an analysis ofposture concludes that patient is prone, the RFID antenna of thepacer/ICD is not activated to transmit power. Techniques for detectingpatient posture and/or changes in posture are set forth in U.S. Pat. No.7,149,579 to Koh et al., entitled “System and Method for DeterminingPatient Posture Based On 3-D Trajectory Using an Implantable MedicalDevice,” which is incorporated by reference herein.

At step 220, the pacer/ICD tracks patient sleep/wake cycles to verifythat the patient is awake. If asleep, then a detection of swallowingmade based upon patient movement or internal sounds is likewise ignored.Examples of sleep detection techniques are set forth in the followingpatents: U.S. Pat. No. 5,476,483, to Bornzin et al., entitled “Systemand Method for Modulating the Base Rate During Sleep for aRate-responsive Cardiac Pacemaker”; U.S. Pat. No. 6,128,534 to Park etal., entitled “Implantable Cardiac Stimulation Device and Method forVarying Pacing Parameters to Mimic Circadian Cycles”; and in U.S. Pat.No. 7,207,947 to Koh et al., entitled “System and Method for DetectingCircadian States Using an Implantable Medical Device.”

If an analysis of patient motion, internal patient sounds, patientposture and patient sleep/wake cycles indicates the patient isswallowing, appropriate internal flags or signals are generated at step222. Otherwise, converse flags or signals are generated at step 224. Inany case, processing returns to FIG. 4 wherein, if the patient is foundto be swallowing, the antenna of pacer/ICD is activated to transmitpower.

2. Exemplary Technique for Monitoring Ingestion of Medications UsingActive RFID

FIG. 6 illustrates an exemplary technique for monitoring medicationintake via pills equipped with active RFID devices, particularly for usewith a pacer/ICD. Many of the techniques of FIG. 6 are similar to thoseof FIG. 4 and only pertinent differences will be described in detail. Inparticular, whereas substantial power savings may be achieved within thetechnique FIG. 6 by limiting the search for passive RFID devices to onlythose periods of time when the patient is swallowing, detection ofactive RFID devices is far less power intensive (at least for thepacer/ICD) and hence, in this example, the detection techniques of FIG.5 are not employed. Beginning at step 300, the pacer/ICD passivelymonitors, via a transceiver or a receiver, for any active RFID signalsgenerated by pills being swallowed. Circuit components for performingthese functions will be described below with reference to FIGS. 10-11.

Again, preferably, low frequency RFID signals are used to allow thesignals to propagate through the tissues of the body. The transmissionpower of the RFID device of the pill is preferably set to the lowestpower level sufficient to ensure that the RFID tag of a pill beingingested will be properly detected by the pacer/ICD. This helps reducepower consumption by the RFID device of the pill as well as reduce therisk of false detections based on RFID pills held outside the body butnot ingested. Optimal power values to be used depend upon the size,shape and orientation of the leads or antennas of the pacer/ICD, theirproximity to the esophagus and stomach, and the characteristics of theintervening tissues, as well as the characteristics of the sensingcircuitry of the pacer/ICD. Routine experimentation may be performed toidentify optimal power levels based upon these parameters. Otherwiseroutine experimentation may be employed to determine appraise powertransmission levels for the active RFID device of the pill. Preferably,following implant of the pacer/ICD, the physician performs tests todetermine the optimal sensitivity level for use with the pacer/ICDsufficient to ensure reliable detection of active RFID signals frompills being ingested by the particular patient in which the pacer/ICDhas been implanted. The pacer/ICD is then programmed to use the optimalsensitivity level. The sensitivity level may be adjusted during afollow-up session if the patient complains that the pacer/ICD has failedto detect medications properly ingested or if the pacer/ICD detectspills that were not ingested but merely held in proximity to the body.

Assuming that an RFID tag has been detected, then processing proceedssubstantially as before. Briefly, at step 302, the pacer/ICD comparesthe RFID tag against the on-board prescription drug/RFID tag database todetermine if it corresponds with any prescription drugs listed therein.If not, a warning is issued at step 304 indicating that the patient hasingested an unknown medication, which has not been prescribed to thepatient. Assuming that the RFID tag is found within the database, thenat step 306, the pacer/ICD compares the medication and dosage of thepill against the on-board patient prescription database to verify thatthe correct drug/dosage as been ingested. If so then, at step 308, thepacer/ICD records the date/time and drug/dosage in the intake recorddatabase. If not, then, at step 310, the pacer/ICD warns the patient ofingestion of the wrong drug or wrong dosage, automatically adjustspacing therapy, and/or controls an implantable drug pump to deliver areserve quantity of the prescribed medication or an alternate acceptablemedication, if available, using techniques already described.

Thus, FIGS. 4-5 illustrate an exemplary passive RFID-based technique,whereas FIG. 6 illustrates an exemplary active RFID-based technique.Preferably, the pacer/ICD is equipped and configured so as to detecteither passive or active RFID tag signals. In other words, the pacer/ICDpassively monitors for any active RFID signals that may be received froma pill being ingested and, at least while the patient is found to beswallowing, actively transmits low-frequency RFID power signals todetect any passive RFID tags. In this manner, the pacer/ICD may be usedin conjunction with either passive or active RFID-equipped prescriptionmedications.

3. Exemplary Technique for Detecting Failure to Ingest Medications

Turning now to FIG. 7, an exemplary technique for determining whether apatient has failed to take a prescribed drug in a timely manner will nowbe described. This technique is used in conjunction with either or bothof the aforementioned techniques. In other words, the pacer/ICD operatesto determine whether a pill being ingested has in fact been prescribedusing the techniques of FIGS. 4-6 and simultaneously operates toidentify circumstances wherein a prescribed pill has not been ingestedwithin an expected time frame using the technique of FIG. 7.

Beginning at step 400, the pacer/ICD periodically accesses the patientprescription database (database 112 of FIG. 3) to identify any currentlyprescribed medications and to read out the corresponding dosages andfrequencies. At step 402, the pacer/ICD then accesses the medicationintake record database (database 114 of FIG. 3) to determine the lastdate and time that each prescribed medication had been ingested. At step404, a target time frame for ingestion of the next dosage of medicationis calculated so that, if patient fails to take a prescribed medicationwithin the target time frame, an appropriate reminder or warning signalmay be issued. In this regard, if the patient takes the next dosage toosoon (i.e. before the beginning of the target time frame), a warningsignal may be issued to that effect. If the patient does not take thenext dosage before the end of the target time frame, a reminder signalmay be issued and, if necessary, therapy may be adjusted to compensatefor failure to take medication.

The determination of the target time frame for a particular prescribedmedication is made based upon the prescribed frequency for thatmedication and the last date/time, if any, that the medication had beeningested. In one example, if the prescribed intake frequency for aparticular drug is “once per day”, the target time frame for nextingestion is calculated to begin 18 hours following the last recordedingestion and to extend until 30 hours following the last recordedingestion. In other words, a 12 hour time frame for ingestion of thenext dosage is defined, which is centered 24 hours following the lastreported ingestion of the medication. In another example, if theprescribed intake frequency for a particular drug is “twice per day”,the target time frame for ingestion of the next dosage begins eighthours following the last recorded ingestion and extends until 16 hoursfollowing that last recorded ingestion. Hence, an eight-hour timeframeis defined, centered 12 hours following the last reported ingestion ofthe medication. These are merely examples. Depending upon the particularimplementation, the time frame may be adjusted so as to exclude periodsof time when the patient is expected to be asleep. In other words, ifthe initially-calculated time frame for ingestion of the next dosagewould require the patient to take the drug during the middle of thenight, the time frame may be adjusted so that warning/reminder signalsare not generated while the patient is asleep (unless the drug is socritical that the patient should be awoken during the night to take themedication.)

Then, at step 406, the pacer/ICD monitors for ingestion of medicationbased upon the RFID tag signals using the techniques discussed above.Assuming the medication is ingested within the target time frame, thepacer/ICD merely updates the medication intake record database, at step410, and returns to step 400 to calculate the next target time frame forthat medication. If, however, the medication was not taken within thetarget time frame, then step 412 is instead performed wherein thepacer/ICD: generates a warning signal indicating the medication wastaken too soon; generates a reminder signals indicating that themedication was not taken within the target time frame; adjusts pacingtherapy in attempt to compensate; and/or delivers a suitable alternatemedication via an implanted drug pump, if so equipped.

Thus, FIG. 7 illustrates a technique for detecting if a patient hasfailed to take prescribed medication in a timely manner or if thepatient has taken the prescribed medication too soon. The steps of theFIG. 7 are preferably performed periodically, e.g. at least once perhour, or more frequently, particularly if medications have beenprescribed that require dosages that are more frequent.

RFID-Equipped Medications

Turning now to FIGS. 8-11, RFID-equipped medications will now bedescribed in greater detail. FIG. 8 illustrates an exemplary gel capsule500 with an RFID device 502 attached thereto. Individual circuits of theRFID device are not shown. As can be seen, the RFID device is wrappedaround the perimeter of the capsule. Hence, in this implementation,circuitry of the RFID device may need to be mounted on a flexiblesubstrate to permit it to conform to the curvature of the capsule.However, if the RFID device is sufficiently small relative to thecapsule, then a flexible substrate is not required. To affix the RFIDdevice to the capsule, a gel layer (not shown) may be formed around theentire capsule/RFID assembly. The gel layer not only holds the RFIDdevice against the capsule but also protects the device from damage ordeterioration and also ensures that the capsule will be easilyswallowable by the patient. Note that, if the capsule is a gel capsulenormally provided with an outer skin, the RFID device may simply beplaced within the outer skin, thus eliminating the need to provide aseparate gel layer specifically for enclosing the RFID device.Alternative techniques may be employed for fixing the device to thecapsule. FIG. 9 illustrates an exemplary tablet 504 with an RFID device506 affixed to a flat side surface thereof. Again, an external gel layer(not shown) may be provided around the entire tablet/RFID assembly forthe affixing the device to the tablet. Other techniques for affixing theRFID device to the tablet may alternatively be employed.

Alternatively, the RFID device may be enclosed within the pill itself,i.e., during manufacture, the pill is formed around the RFID device.This eliminates the need to affix the RFID device to an external surfaceof the pill. However, affixing the device to the outside of the pill ispreferred for several reasons. With the device attached to the outsideof the pill, fabrication techniques for manufacturing the pill need notbe modified to account for the device. Instead, the device is merelyattached after pill manufacture. Moreover, with the RFID device on theoutside surface of the pill, the pill can be easily inspected to verifythat the RFID device is attached, and the device can also be visuallyinspected for possible damage. In addition, with the device enclosedwithin the pill, the pill itself may interfere withtransmission/reception of signals, possibly requiring higher signaltransmission power.

With present technologies, the circuitry for an RFID device is readilyaccommodated within an area 2.5 mm×2.5 mm square, including integratedantenna. Routine experimentation may be performed to determine if adevice of that size has sufficient transmission power for the purposesof the invention. If not, larger and more powerful RFID devices aresimply used. For any pill that may be too small to have a RFID deviceattached to its side surface, the pill may instead be attached to theside surface of the RFID device, with the pill/RFID assembly thenenclosed in a sufficient quantity of gel material to ensure that theentire assembly is easily indigestible.

As noted above, the RFID devices are preferably coated with a materialto render the device biocompatible and non-digestible. In this manner,the RFID device is eventually eliminated from the body as waste afterthe medication of the pill has been digested. In one example, the RFIDdevice is potted in a ceramic or similar substance to ensure nobiocompatibility problems. Parylene may also be suitable, as well asselected plastics. Techniques for encapsulating an RFID device forinsertion into biological samples or corrosive environments arediscussed in U.S. Pat. No. 5,963,132 to Yoakum, entitled “EncapsulatedImplantable Transponder.”

Functional components for passive and active RFID devices (and theimplantable device that receives signals therefrom) are illustratedwithin FIGS. 10 and 11. Briefly, passive RFID device 520 of FIG. 10includes an RF rectifier 522 (which is used as a power supply), an IDcircuit 524 (which stores the ID of the RFID tag), control logic 526 andan on-chip antenna 528. The ID circuit 524 may be a read-only memory(ROM) circuit. The medication to which the RFID device is attached isillustrated by way of block 530. The implanted device includes anantenna 534, a transceiver 536 and control logic 538 for controllingtransmission and reception of signals from the RFID device. Thesecomponents are in addition to normal functions of the device, such aspacing functions and the like, which are collectively represented byblock 540. Briefly, in the passive RFID implementation, the controllogic (538) of the implanted device controls the transceiver to deliveralternating current (AC) power to antenna 534 for transmission via an RFlink to the antenna of the RFID device. AC power received by the on-chipantenna is rectified by the RF rectifier, which is then routed to thecontrol logic of the RFID device, which uses the power to access the IDROM to readout the RFID tag and to transmit the RFID tag via the on-chipantenna to the implanted device over the RF link. As noted above, lowfrequencies are preferably used. The RFID ID tag signal transmitted bythe RFID device is received by the antenna of the implanted device anddecoded by its transceiver. The control logic of the implanted deviceuses the RFID tag in accordance with the techniques described above toidentify the particular medication being ingested, generate anynecessary warning/reminder signals, adjust device functionality, etc.

Functional components for an active RFID device (and the implantabledevice that receives signals therefrom) is illustrated within FIG. 11.Many of the components are the same or similar to those of FIG. 10 willnot be re-described. Briefly, active RFID device 550 of FIG. 11 includesan on-board battery 552, an ID circuit 554, control logic 556 andon-chip antenna 558. Whereas the antenna of the passive RFID device ofFIG. 10 must be capable of receiving power from the pacer/ICD as well astransmitting RFID tag signals, with the active device of FIG. 11, poweris instead provided by the on-board battery and hence antenna 558 isused only to transmit data. Accordingly, antenna 558 of FIG. 10 maydiffer in size and configuration from antenna 528 of FIG. 11. Themedication to which the RFID device is attached is illustrated by way ofblock 560. The implanted device 562 includes an antenna 564, atransceiver 566 and control logic 568 for controlling reception ofsignals from the RFID device. These components are in addition tocomponents performing the normal functions of the device, such as pacingfunctions and the like, which are collectively represented by block 570.Whereas antenna 534 of FIG. 10 for use with passive RFID devices must becapable of transmitting power to the RFID device, antenna 564 of FIG. 11need only receive signals from the RFID device. Accordingly, if desired,antenna 564 of FIG. 11 may be configured with a different size and shapefrom antenna 534 of FIG. 10 so as to be optimized for receiving RFIDsignals only. Also, the transceiver and control logic of the activeconfiguration of FIG. 11 may differ from corresponding components of thepassive configuration of FIG. 10. Preferably, however, the antenna,transceiver and control logic of the implanted device are configured soas to operate with both passive and active RFID devices.

Exemplary Pacer/ICD

The aforementioned techniques may be exploited in connection with a widevariety of implantable devices. For the sake of completeness, a detaileddescription of a suitable pacer/ICD will now be provided with referenceto FIGS. 12 and 13.

Referring first to FIG. 12, the figure provides a simplified blockdiagram of the pacer/ICD, which is a multi-chamber stimulation devicecapable of treating both fast and slow arrhythmias with stimulationtherapy, including cardioversion, defibrillation, and pacing stimulation(as well as capable of detecting RFID tags, tracking medication intakebased on the tags, controlling the generation of reminder/warningsignals and adjusting therapy in response thereto.) To provide atrialchamber pacing stimulation and sensing, pacer/ICD 10 is shown inelectrical communication with a heart 612 by way of a left atrial lead620 having an atrial tip electrode 622 and an atrial ring electrode 623implanted in the atrial appendage. Pacer/ICD 10 is also in electricalcommunication with the heart by way of a right ventricular lead 630having, in this embodiment, a ventricular tip electrode 632, a rightventricular ring electrode 634, a right ventricular (RV) coil electrode636, and a superior vena cava (SVC) coil electrode 638. Typically, theright ventricular lead 630 is transvenously inserted into the heart soas to place the RV coil electrode 636 in the right ventricular apex, andthe SVC coil electrode 638 in the superior vena cava. Accordingly, theright ventricular lead is capable of receiving cardiac signals, anddelivering stimulation in the form of pacing and shock therapy to theright ventricle.

To sense left atrial and ventricular cardiac signals and to provide leftchamber pacing therapy, pacer/ICD 10 is coupled to a “coronary sinus”lead 624 designed for placement in the “coronary sinus region” via thecoronary sinus os for positioning a distal electrode adjacent to theleft ventricle and/or additional electrode(s) adjacent to the leftatrium. As used herein, the phrase “coronary sinus region” refers to thevasculature of the left ventricle, including any portion of the coronarysinus, great cardiac vein, left marginal vein, left posteriorventricular vein, middle cardiac vein, and/or small cardiac vein or anyother cardiac vein accessible by the coronary sinus. Accordingly, anexemplary coronary sinus lead 624 is designed to receive atrial andventricular cardiac signals and to deliver left ventricular pacingtherapy using at least a left ventricular tip electrode 626, left atrialpacing therapy using at least a left atrial ring electrode 627, andshocking therapy using at least a left atrial coil electrode 628. Withthis configuration, biventricular pacing can be performed. Although onlythree leads are shown in FIG. 12, it should also be understood thatadditional stimulation leads (with one or more pacing, sensing and/orshocking electrodes) may be used in order to efficiently and effectivelyprovide pacing stimulation to the left side of the heart or atrialcardioversion and/or defibrillation. The leads are also employed forsensing ID tag signals from medications equipped with active IDtransmitters.

A simplified block diagram of internal components of pacer/ICD 10 isshown in FIG. 13. While a particular pacer/ICD is shown, this is forillustration purposes only, and one of skill in the art could readilyduplicate, eliminate or disable the appropriate circuitry in any desiredcombination to provide a device capable of treating the appropriatechamber(s) with cardioversion, defibrillation and pacing stimulation aswell as providing for the aforementioned apnea detection and therapy.The housing 640 for pacer/ICD 10, shown schematically in FIG. 13, isoften referred to as the “can”, “case” or “case electrode” and may beprogrammably selected to act as the return electrode for all “unipolar”modes. The housing 640 may further be used as a return electrode aloneor in combination with one or more of the coil electrodes, 628, 636 and638, for shocking purposes. The housing 640 further includes a connector(not shown) having a plurality of terminals, 642, 643, 644, 646, 648,652, 654, 656 and 658 (shown schematically and, for convenience, thenames of the electrodes to which they are connected are shown next tothe terminals). As such, to achieve right atrial sensing and pacing, theconnector includes at least a right atrial tip terminal (A_(R) TIP) 642adapted for connection to the atrial tip electrode 622 and a rightatrial ring (A_(R) RING) electrode 643 adapted for connection to rightatrial ring electrode 643. To achieve left chamber sensing, pacing andshocking, the connector includes at least a left ventricular tipterminal (V_(L) TIP) 644, a left atrial ring terminal (A_(L) RING) 646,and a left atrial shocking terminal (A_(L) COIL) 648, which are adaptedfor connection to the left ventricular ring electrode 626, the leftatrial tip electrode 627, and the left atrial coil electrode 628,respectively. To support right chamber sensing, pacing and shocking, theconnector further includes a right ventricular tip terminal (V_(R) TIP)652, a right ventricular ring terminal (V_(R) RING) 654, a rightventricular shocking terminal (R_(V) COIL) 656, and an SVC shockingterminal (SVC COIL) 658, which are adapted for connection to the rightventricular tip electrode 632, right ventricular ring electrode 634, theRV coil electrode 636, and the SVC coil electrode 638, respectively.Separate terminals (not shown) may be provided for connecting theexternal RFID device 12, the implanted warning/reminder device 18 andthe implanted drug pump 24, which are instead shown coupled directly tointernal functional components of the pacer/ICD that control thesedevices.

At the core of pacer/ICD 10 is a programmable microcontroller 660, whichcontrols the various modes of stimulation therapy. As is well known inthe art, the microcontroller 660 (also referred to herein as a controlunit) typically includes a microprocessor, or equivalent controlcircuitry, designed specifically for controlling the delivery ofstimulation therapy and may further include RAM or ROM memory, logic andtiming circuitry, state machine circuitry, and I/O circuitry. Typically,the microcontroller 660 includes the ability to process or monitor inputsignals (data) as controlled by a program code stored in a designatedblock of memory. The details of the design and operation of themicrocontroller 660 are not critical to the invention. Rather, anysuitable microcontroller 660 may be used that carries out the functionsdescribed herein. The use of microprocessor-based control circuits forperforming timing and data analysis functions are well known in the art.

As shown in FIG. 13, an atrial pulse generator 670 and aventricular/impedance pulse generator 672 generate pacing stimulationpulses for delivery by the right atrial lead 620, the right ventricularlead 630, and/or the coronary sinus lead 624 via an electrodeconfiguration switch 674. It is understood that in order to providestimulation therapy in each of the four chambers of the heart, theatrial and ventricular pulse generators, 670 and 672, may includededicated, independent pulse generators, multiplexed pulse generators orshared pulse generators. The pulse generators, 670 and 672, arecontrolled by the microcontroller 660 via appropriate control signals,676 and 678, respectively, to trigger or inhibit the stimulation pulses.

The microcontroller 660 further includes timing control circuitry (notseparately shown) used to control the timing of such stimulation pulses(e.g., pacing rate, atrio-ventricular (AV) delay, atrial interconduction(A-A) delay, or ventricular interconduction (V-V) delay, etc.) as wellas to keep track of the timing of refractory periods, blankingintervals, noise detection windows, evoked response windows, alertintervals, marker channel timing, etc., which is well known in the art.Switch 674 includes a plurality of switches for connecting the desiredelectrodes to the appropriate I/O circuits, thereby providing completeelectrode programmability. Accordingly, the switch 674, in response to acontrol signal 680 from the microcontroller 660, determines the polarityof the stimulation pulses (e.g., unipolar, bipolar, combipolar, etc.) byselectively closing the appropriate combination of switches (not shown)as is known in the art.

Atrial sensing circuits 682 and ventricular sensing circuits 684 mayalso be selectively coupled to the right atrial lead 620, coronary sinuslead 624, and the right ventricular lead 630, through the switch 674 fordetecting the presence of cardiac activity in each of the four chambersof the heart and for sensing RFID tag signals received from active RFIDdevices. Accordingly, the atrial (ATR. SENSE) and ventricular (VTR.SENSE) sensing circuits, 682 and 684, may include dedicated senseamplifiers, multiplexed amplifiers or shared amplifiers. The switch 674determines the “sensing polarity” of the cardiac signal by selectivelyclosing the appropriate switches, as is also known in the art. In thisway, the clinician may program the sensing polarity independent of thestimulation polarity. Each sensing circuit, 682 and 684, preferablyemploys one or more low power, precision amplifiers with programmablegain and/or automatic gain control, bandpass filtering, and a thresholddetection circuit, as known in the art, to selectively sense the cardiacsignal of interest. The automatic gain control enables pacer/ICD 10 todeal effectively with the difficult problem of sensing the low amplitudesignal characteristics of atrial or ventricular fibrillation. Theoutputs of the atrial and ventricular sensing circuits, 682 and 684, areconnected to the microcontroller 660 which, in turn, are able to triggeror inhibit the atrial and ventricular pulse generators, 670 and 672,respectively, in a demand fashion in response to the absence or presenceof cardiac activity in the appropriate chambers of the heart.

For arrhythmia detection, pacer/ICD 10 utilizes the atrial andventricular sensing circuits, 682 and 684, to sense cardiac signals todetermine whether a rhythm is physiologic or pathologic. As used herein“sensing” is reserved for the noting of an electrical signal, and“detection” is the processing of these sensed signals and noting thepresence of an arrhythmia. The timing intervals between sensed events(e.g., P-waves, R-waves, and depolarization signals associated withfibrillation which are sometimes referred to as “F-waves” or“Fib-waves”) are then classified by the microcontroller 660 by comparingthem to a predefined rate zone limit (i.e., bradycardia, normal, atrialtachycardia, atrial fibrillation, low rate VT, high rate VT, andfibrillation rate zones) and various other characteristics (e.g., suddenonset, stability, physiologic sensors, and morphology, etc.) in order todetermine the type of remedial therapy that is needed (e.g., bradycardiapacing, antitachycardia pacing, cardioversion shocks or defibrillationshocks).

Cardiac signals are also applied to the inputs of an analog-to-digital(A/D) data acquisition system 690. The data acquisition system 690 isconfigured to acquire intracardiac electrogram signals, convert the rawanalog data into a digital signal, and store the digital signals forlater processing and/or telemetric transmission to an external device702. The data acquisition system 690 is coupled to the right atrial lead620, the coronary sinus lead 624, and the right ventricular lead 630through the switch 674 to sample cardiac signals across any pair ofdesired electrodes. The microcontroller 660 is further coupled to amemory 694 by a suitable data/address bus 696, wherein the programmableoperating parameters used by the microcontroller 660 are stored andmodified, as required, in order to customize the operation of pacer/ICD10 to suit the needs of a particular patient. Such operating parametersdefine, for example, pacing pulse amplitude or magnitude, pulseduration, electrode polarity, rate, sensitivity, automatic features,arrhythmia detection criteria, and the amplitude, waveshape and vectorof each shocking pulse to be delivered to the patient's heart withineach respective tier of therapy. Other pacing parameters include baserate, rest rate and circadian base rate.

Advantageously, the operating parameters of the implantable pacer/ICD 10may be non-invasively programmed into the memory 694 through a telemetrycircuit 700 in telemetric communication with the external device 702,such as a programmer, transtelephonic transceiver or a diagnostic systemanalyzer. The telemetry circuit 700 is activated by the microcontrollerby a control signal 706. The telemetry circuit 700 advantageously allowsintracardiac electrograms and status information relating to theoperation of pacer/ICD 10 (as contained in the microcontroller 660 ormemory 694) to be sent to the external device 702 through an establishedcommunication link 704. Pacer/ICD 10 further includes an accelerometeror other physiologic sensor 708, commonly referred to as a“rate-responsive” sensor because it is typically used to adjust pacingstimulation rate according to the exercise state of the patient.However, the physiological sensor 708 may, depending upon itscapabilities, further be used to detect changes in cardiac output,changes in the physiological condition of the heart, or diurnal changesin activity (e.g., detecting sleep and wake states) and to detectarousal from sleep. Accordingly, the microcontroller 660 responds byadjusting the various pacing parameters (such as rate, AV Delay, V-VDelay, etc.) at which the atrial and ventricular pulse generators, 670and 672, generate stimulation pulses. While shown as being includedwithin pacer/ICD 10, it is to be understood that the accelerometer 708may also be external to pacer/ICD 10, yet still be implanted within orcarried by the patient. A common type of rate responsive sensor is anactivity sensor incorporating an accelerometer or a piezoelectriccrystal, which is mounted within the housing 640 of pacer/ICD 10. Othertypes of physiologic sensors are also known, for example, sensors thatsense the oxygen content of blood, respiration rate and/or minuteventilation, pH of blood, ventricular gradient, etc. An accelerometer ispreferred as it allows patient movement and patient posture to bedetected for use in verifying patient swallowing to aid in detection ofRFID signals. An acoustic sensor 709 is preferably also employed forthis purpose.

The pacer/ICD additionally includes a battery 710, which providesoperating power to all of the circuits shown in FIG. 13. The battery 710may vary depending on the capabilities of pacer/ICD 10. If the systemonly provides low voltage therapy, a lithium iodine or lithium copperfluoride cell may be utilized. For pacer/ICD 10, which employs shockingtherapy, the battery 710 should be capable of operating at low currentdrains for long periods, and then be capable of providing high-currentpulses (for capacitor charging) when the patient requires a shock pulse.The battery 710 should also have a predictable discharge characteristicso that elective replacement time can be detected. Accordingly,pacer/ICD 10 is preferably capable of high voltage therapy and batteriesor other power sources appropriate for that purpose are employed.

As further shown in FIG. 13, pacer/ICD 10 is shown as having animpedance measuring circuit 712 which is enabled by the microcontroller660 via a control signal 714. Other uses for an impedance measuringcircuit include, but are not limited to, lead impedance surveillanceduring the acute and chronic phases for proper lead positioning ordislodgement; detecting operable electrodes and automatically switchingto an operable pair if dislodgement occurs; measuring respiration orminute ventilation; measuring thoracic impedance for determining shockthresholds; detecting when the device has been implanted; measuringstroke volume; and detecting the opening of heart valves, etc. Theimpedance measuring circuit 120 is advantageously coupled to the switch74 so that any desired electrode may be used.

In the case where pacer/ICD 10 is intended to operate as an implantablecardioverter/defibrillator (ICD) device, it detects the occurrence of anarrhythmia, and automatically applies an appropriate electrical shocktherapy to the heart aimed at terminating the detected arrhythmia. Tothis end, the microcontroller 660 further controls a shocking circuit716 by way of a control signal 718. The shocking circuit 716 generatesshocking pulses of low (up to 0.5 joules), moderate (0.5-10 joules) orhigh energy (11 to 40 joules), as controlled by the microcontroller 660.Such shocking pulses are applied to the heart of the patient through atleast two shocking electrodes, and as shown in this embodiment, selectedfrom the left atrial coil electrode 628, the RV coil electrode 636,and/or the SVC coil electrode 638. The housing 640 may act as an activeelectrode in combination with the RV electrode 636, or as part of asplit electrical vector using the SVC coil electrode 638 or the leftatrial coil electrode 628 (i.e., using the RV electrode as a commonelectrode). Cardioversion shocks are generally considered to be of lowto moderate energy level (so as to minimize pain felt by the patient),and/or synchronized with an R-wave and/or pertaining to the treatment oftachycardia. Defibrillation shocks are generally of moderate to highenergy level (i.e., corresponding to thresholds in the range of 5-40joules), delivered asynchronously (since R-waves may be toodisorganized), and pertaining exclusively to the treatment offibrillation. Accordingly, the microcontroller 660 is capable ofcontrolling the synchronous or asynchronous delivery of the shockingpulses.

Microcontroller 60 also includes an RFID signal-based medication intakemonitor 701 for automatically monitoring the intake of drugs prescribedto the patient using the techniques described above. In this regard, themedication intake monitor 701 is operative to control RFID tag detectionbased on signals received from the RFID transceiver via either active orpassive RFID techniques, already described. For passive RFID, themedication intake monitor processes data received from accelerometer 708and the acoustic sensor 709 to detect when the patient is in the act ofswallowing and, if so, activates RFID transceiver 12 to transmit powerto any RFID device being swallowed at that time. Responsive RFIDsignals, if any, sensed by RFID transceiver 12 are processed bymedication intake monitor 701 to decode the RFID tag. For active RFID,the RFID transceiver monitors for RFID signals from any active RFIDbeing ingested and forwards the signals to medication intake monitor todecode the ID tag. The controller uses the techniques described above toverify that the RFID tag identities a drug that had been prescribed tothe patient and also periodically identifies any drugs that had beenprescribed but had not been ingested in a timely manner. Awarning/reminder controller 703 operates to generate appropriatereminder or warning signals, using the techniques described above, forforwarding to the implanted reminder/warning device 18 or to the bedsidewarning/reminder system 22. A medication-base therapy controller 705operates to control therapy in response to drug intake (or lack thereofvia implanted drug pump 24 or via pacing using the leads of thepacer/ICD. In an alternative embodiment, analysis of the RFID signals isperformed by the external programmer 702 or the bedside monitoringsystem 22 and so medication intake monitor 701 merely forwards RFID tagdata via telemetry circuit 700 to the appropriate external device.

What have been described thus far are primarily techniques for use withmedications tagged with RFID devices. Other types of EID devices (i.e.non-RF EID devices) may instead be used. In the following, analternative implementation is discussed that exploits signals sent viabiphasic current pulses that are conducted through patient tissue. Inother words, instead of using RF signals (which propagate aselectromagnetic waves) to transmit data from the pill to the implantedsystem, the alternative implementation instead uses pulses of electricalcurrent that are conducted through the tissues of the body. Many of thefeatures of the alternative implementation are the same as with theRFID-based implantation already described and so the alternativeimplementation will only be summarized.

Biphasic Current Pulse-Based Medication Intake Monitoring System

FIG. 14 illustrates an implantable medical system 808 having a pacer/ICD810 capable of detecting the ingestion of medication 812 via an ID tagsignal transmitted in the form of biphasic current pulses conductedthrough the tissues of the body to a set of leads 814 of the implanteddevice. (Only two leads are shown in FIG. 14. A full set of leads isillustrated in FIG. 12.) The medication being ingested includes an EIDdevice 816, which includes circuitry for storing the ID tag and forgenerating the biphasic current pulses. The pacer/ICD uses the ID tag toverify the correct drug/dosage of ingested medications and thengenerates and forwards appropriate warning signals to a bedsidemonitor/warning system 22, in accordance with techniques alreadydescribed. Pacing therapy may also be adjusted based on whether thecorrect drug/dosage of the medications has been ingested. Although notshown in FIG. 14, an implantable warning device may also be provided, asshown in FIG. 1, for delivering warning signals internally. In addition,an implantable drug pump, also shown in FIG. 1, may be provided fordelivering medications directly to the patient. Unlike the embodiment ofFIG. 1, no RFID transceiver is used.

The system of FIG. 14 is a passive system, in that the EID device of thepill being ingested generates the biphasic current pulses using powerfrom an on-board battery. The ID tag is encoded for transmission as asequence of pulses, using otherwise conventional data encoding andtransmission techniques. The leads of the device are used to detect thecurrent pulses so that the ID can be decoded. That is, a pair ofelectrodes within the leads, such as the right and left ventricular tipelectrodes, is selected for use as a detection “antenna” for detectingthe current pulses. Alternatively, the device may be used as one of theelectrodes. In any case, otherwise conventional techniques for use indetecting thoracic impedance using pacing leads may be used fordetecting the current pulses as well. Impedance detection techniques areset forth in, for example, U.S. Pat. No. 6,658,294 to Zadeh, et al.,entitled “Implantable Cardiac Device Having an Impedance MonitoringCircuit and Method.” Preferably, normal pacing and sensing functions ofthe leads are temporarily Suspended while the leads are used to detectcurrent pulses, i.e. the normal atrial and ventricular sense amplifiersare blanked during the ID receive time to prevent possible false P and Rsensing and subsequent inadvertent pacing inhibition. The techniquesdescribed above for use in detecting when the patient is swallowing arepreferably employed and the leads are only enabled for ID detectionduring periods of time when it appears the patient may be in the act ofswallowing medication.

Functional components for EID device 816 (and the implantable devicethat receives signals therefrom) are illustrated within FIG. 15. Many ofthe components are the same or similar to those of the active RFIDimplementation of FIG. 11 and will not be re-described. Briefly,biphasic current EID device 816 includes an on-board battery 952, an IDcircuit 954 and control logic 956. Rather than employing an on-chipantenna, EID device 950 instead uses a biphasic current pulse generator958, which includes a pair of electrodes spaced as widely apart on themedication as possible. The medication to which the EID device isattached is illustrated by way of block 960. The implanted device,rather than employing an RFID transceiver as in the RFID embodimentsdescribed above, instead uses one or more cardiac pacing leads 814 tosense the current pulse signals. A sense block 966 is provided forsensing current pulse signals picked up by the leads, including IDsignals. Sense block 966 is separate from the sense amplifiers that areused for sensing electrical cardiac signals (i.e. sense amplifiers 682and 684 discussed above). In other words, the implanted device includesa separate set of sense amplifiers specifically configured for sensingthe current pulses. A decoder and control logic unit 968 decodes thecurrent pulse ID signals to identify the ID tag. The decoder and controllogic unit then uses the ID tag in accordance with the techniquesdescribed above to identify the particular medication being ingested,generate any necessary warning/reminder signals, adjust devicefunctionality, etc. Normal functions of the device, such as normalsensing and pacing functions, are collectively represented by block 970.

The various functional components of the exemplary system may beimplemented using any appropriate technology including, for example,microprocessors running software programs or application specificintegrated circuits (ASICs) executing hard-wired logic operations. Theexemplary embodiments of the invention described herein are merelyillustrative of the invention and should not be construed as limitingthe scope of the invention.

1. In an implantable medical device, a method for monitoring theingestion of pills by a patient, the method comprising: sensing a signaltransmitted by an individual pill being ingested; detecting ingestion ofthe pill based on the sensed signal; automatically determining whetherthe pill is prescribed to the patient; and generating a warning signalif the pill is not prescribed to the patient.
 2. The method of claim 1wherein the individual pill is equipped with radio frequencyidentification (RFID) device and wherein sensing the signal transmittedby the pill comprises sensing an RFID signal transmitted by the RFIDdevice of the pill.
 3. The method of claim 2 wherein the RFID device isan active ID device and wherein sensing the signal transmitted by thepill comprises sensing active ID signals transmitted by the ID device.4. The method of claim 2 wherein the individual pill is equipped with apassive RFID device and wherein sensing signals comprises: transmittinga power signal to the passive RFID device of the pill; and receiving aresponsive signal returned by the passive RFID device of the pill. 5.The method of claim 4 wherein the implantable system is equipped todetect and classify patient movement and wherein transmitting a powersignal to the passive RFID device is triggered by detection of patientmotion that is consistent with the swallowing of a pill.
 6. The methodof claim 4 wherein the implantable system is equipped to detect internalpatient sounds and wherein transmitting a power signal to the passiveRFID device is triggered by detection of sounds consistent withswallowing a pill.
 7. The method of claim 4 wherein the implantablesystem is equipped to detect and classify patient posture and whereintransmitting a power signal to the passive RFID device is not performedunless patient posture is consistent with the swallowing of a pill. 8.The method of claim 4 wherein the implantable system is equipped todetect patient sleep and wherein transmitting a power signal to thepassive RFID device is not performed if the patient is asleep.
 9. Themethod of claim 2 wherein the RFID signal includes an RFID tagsufficient to identify the medication being ingested and whereindetecting ingestion of a pill comprises: decoding the RFID tag of theRFID signal; comparing the decoded RFID tag against a database listingindividual RFID tags and the particular medications associatedtherewith; and generating a signal indicative of the particularmedication being ingested if the decoded RFID tag matches an RFID tagstored in the database.
 10. The method of claim 1 wherein determiningwhether the pill is prescribed to the patient comprises comparing thepill against a database listing medications prescribed to the patient.11. The method of claim 1 wherein the implanted system includes animplanted warning device for generating a perceptible signal and whereingenerating a warning signal is performed by activating the implantedwarning device.
 12. The method of claim 1 wherein the implanted systemis used in conjunction with an external warning device and whereingenerating a warning signal is performed by transmitting a warningsignal to the external warning device.
 13. The method of claim 9 whereinthe RFID tag is also sufficient to identify the dosage of the medicationbeing ingested and wherein detecting ingestion of a pill also comprisesgenerating a signal indicative of the dosage being ingested.
 14. Themethod of claim 13 further comprising: determining whether the dosagebeing ingested is a dosage prescribed to the patient; and generating awarning signal if the dosage being ingested is not the dosage prescribedto the patient.
 15. The method of claim 14 wherein determining whetherthe dosage being ingested is the dosage prescribed to the patientcomprises comparing the dosage being ingested against a database listingthe dosage prescribed to the patient for the particular medication beingingested.
 16. In an implantable medical device, a method for monitoringthe ingestion of pills by a patient, the method comprising: sensingsignals transmitted by individual pills being ingested to detectingestion of the pills; comparing the ingestion of the pills with aschedule; and based on the comparison, determining whether the patienthas failed to take any prescribed medications.
 17. The method of claim16 wherein determining whether the patient has failed to take prescribedmedications comprises: identifying medications that have been taken bythe patient, if any, based on signals transmitted by individual pillsbeing ingested that contain the medications; accessing a databaselisting medications prescribed to the patient; identifying prescribedmedications that have not been taken based on a comparison of themedications prescribed to the patient in comparison with medications, ifany, taken by the patient.
 18. The method of claim 16 and furthercomprising generating a warning signal in response to the patientfailing to take any prescribed medications.
 19. An implantable systemfor use in monitoring the ingestion of pills by a patient, the systemcomprising: a receiver that senses signals transmitted bysignal-transmitting pills being ingested by the patient; and amedication monitoring controller that determines whether the patient hasfailed to take any prescribed medications based on signals sensed by thereceiver and based on a comparison with a schedule stored by themedication monitoring controller.
 20. The system of claim 19 wherein themedication monitoring controller generates a warning signal in responseto the patient failing to take any prescribed medications.